1. Field of the Invention
The present invention relates to the field of integrated circuits. More specifically, the present invention relates to a circuit for determining if the operating voltage of a first circuit exceeds the power supply value of a second circuit.
2. Background of the Invention
The integrated circuit business and semiconductor industry continually strive to reduce the cost and power of its products while improving their performance. Integrated circuit products include, for example, microprocessors, memories, programmable logic, and programmable controllers. Price reduction is achieved through scaled processes that reduce size and increase yields. Power reduction has been accomplished through, for example, circuit design techniques, power management schemes, and parasitic scaling.
Semiconductor integrated circuit technology is developing rapidly. One consequence of the rapid development is that modern integrated circuit devices are being designed to operate from system supply voltages that are constantly becoming lower. For example, many older electrical circuits were designed to operate from a 5 Volt supply. However, newer devices are designed to operate from voltages such as 3.3 Volts or lower.
Despite this trend, all manufacturers have not switched over to the lower power supply simultaneously. Therefore, integrated circuits must still supply higher operating voltages so that older electrical circuits can operate efficiently. Mixed voltage circuits require “overvoltage” tolerant interfaces that allow devices operating from a lower supply voltage to interface with other devices operating at a higher supply voltage.
Many newer circuits may not be tolerant of signals provided by older circuits. At the very least, signal integrity can be compromised. In a worst case scenario, circuit damage and system malfunction can occur unless the incompatible operation is prevented or controlled. In order to facilitate compatible operation between newer and older circuits, a circuit must first detect differences between the supply voltage and the operating voltage of a given circuit. Compensation circuits can then be designed to accommodate for these differences.
A continuing need exists for a simple overvoltage detection circuit that can be adapted for use in a variety of applications.